I just used some rattle cans that I had on hand, a Plasti-kote grey metal primer and Plasti-kote Rust Not in gloss black. Since I had the entire front end stripped down during the inspection of the new-to-me '96 ST, it was easy to paint the parts up, while off the bike.
The bars already have a greenish coat of primer paint, so I just laid the black on top of that and I used the grey primer on the bare aluminum top fork bridge and associated bar clamp parts. Rather than pull the ignition switch off the bike, I masked the switch and sprayed only the small section that protrudes above the fork bridge.
One thing I discovered in mounting the risers was that with the Rox name facing outwards, the bars did not sit entirely flat within the upper clamps, as the bend in the bars *just* caught that point of where the outer edge of the clamp sat. For that reason, I mounted the risers with the name facing inwards, which gives a much better grip for the clamps. The second pic below shows a bit more detail of the hoses and the risers for you. At this point in the process, I hadn't yet determined that the clutch hose would tend to catch the bridge at the left fork corner, so I removed that clutch hose clamp located on the frame and instead used the black plastic clamp that had been on the front brake hose and clamped the clutch hose to the upper fork tube, as seen in the first photo.
If you do the same dismantling, it is an excellent time to inspect, clean, lube and re-torque the steering head bearings. Mine still had the ball bearings and the races and balls were all in very good condition. As an aside to this, over the many years of much "wobble" and "headshake" teeth gnashing and debate, I have come to believe that the vast majority of those issues would never have surfaced if every new ST1100 was properly serviced at its first Honda mandated service interval, which specified a re-torquing of the steering head bearings. Being a bit of a tear down expense, I doubt that service was performed on many ST's early in their life.